The invention relates generally to multi-battery systems and, more particularly, to a temperature control system for multiple batteries.
A wide variety of devices, apparatuses, or systems use multiple batteries to power various aspects and/or components thereof. Often, such batteries operate optimally within a defined temperature range. That is, batteries of such devices operate optimally when the temperatures of such batteries are kept within a determined or defined temperature operating range. Further, two or more batteries of such devices may have preferred temperature operating ranges that differ from one another. To maintain operating temperatures of batteries, energy is often consumed for heating and cooling purposes.
Multi-battery systems in vehicles such as a battery electric vehicle (BEV), a hybrid-electric vehicle (HEV), or a plug-in hybrid electric vehicle (PHEV) generally include an energy storage system capable of operation over a wide range of environmental temperatures due to variation in ambient temperature. Further, “under-the-hood” systems of such vehicles, such as an internal combustion engine (ICE) and/or other adjacent propulsion and auxiliary components, often cause further temperature variations. Consumers, however, often expect the performance of an electric or hybrid electric propelled vehicle to remain relatively constant irrespective of temperature of the energy storage unit and propulsion drive system.
Many vehicles such as the BEV, HEV, and the PHEV typically use energy storage systems that are capable of producing rated power over a rather narrow environmental temperature range. Depending on the energy storage technology (e.g., lead-acid, Ni-MH, and Li-Ion), output power during discharge is often de-rated or limited when storage temperatures fall to or below approximately zero degrees Celsius, and for some technologies, the battery is not utilized below approximately negative twenty degrees Celsius. Similarly, the power level allowed to recharge the batteries, either by the utility grid to a BEV or PHEV or by regenerative braking, is also often limited at low ambient temperatures. Further, many multi-battery systems rely on batteries have differing optimal operating temperature ranges. For example, a hybrid-electric propulsion system may rely on a high-temperature battery that optimally operates in a temperature range from 270-350 degrees Celsius while also relying on an ambient temperature battery that optimally operates in a temperature range from 0-35 degrees Celsius.
To address operating temperatures of batteries in multi-battery systems, systems have been created that rely on a combination of resistive heaters coupled to each battery in such multi-battery systems and utilization of battery containment boxes that provide thermal insulation. The resistive heaters are then used to ensure that the batteries of such systems are kept within their optimal operating temperature ranges. Such heaters, however, consume electrical power. As such, often an additional battery is added to such systems to power the heaters. However, the additional weight that comes with the additional battery often diminishes vehicle and/or battery performance and often results in inefficiencies. Another solution has been to oversize the traction batteries of systems, such as in an HEV, to provide sufficient power for operation at low ambient temperatures when the battery is forced to operate at temperatures below its optimal operating temperature range. Since the traction battery is oversized, it is able to produce rated power during discharge and also to accept charge power during regenerative braking operation or engine charging in a hybrid vehicle. However, as with the additional battery scenario described above, the added weight of the oversized battery can cause diminished performance and other inefficiencies of such systems.
As such, it may be desirable to have a system that has aspects and features that differ from those that are currently available and that solves at least the aforementioned problems. Further, it may be desirable to have a method that differs from those methods that are currently available.